Craters
on Earth
Almost everyone knows about Meteor Crater in northern Arizona. Although
it is nearly a mile across it is tiny compared to the craters seen
on other planets. Does Earth have any big craters? It was not until
we began to look at Earth using satellites that we began to see
lots of big impact craters on Earth--about 150 are now known. This
map shows the locations of some of them. Meteor
Crater. Photo courtesy of D. Reddy.

Test your skill
at finding impact craters! Click on the numbered squares to get
a satellite image of that area of the Earth. On the image that appears,
see if you can find any impact craters.

You will find
that some craters are easy to locate, but some are not. Why are
Earth's craters so hard to find sometimes? Most craters on the Moon
and other planets are very, very old. Since craters are made by
objects crashing into a planet's surface, each time a crater is
formed there is one less object in space available to form another
crater. Most of the objects that could make craters did so a long
time ago, so now most of these objects are gone! Only a few objects
remain that could have hit the planets
to form new craters. Look carefully at the map above. Are most of
the craters on young land or old land?

The surface
of Earth was once covered
with large craters. But the Earth's surface has an active atmosphere.
Wind and rain quickly erode craters and plate
tectonics buries them. So only a few craters made in the last
few hundred million years can be found at all!

But did an impact
kill the dinosaurs? If you haven't already, select square #3 (the
Yucatan Peninsula) on the Finder Map to see a possible culprit!